Golang runtime/trace: set the v2 tracer as the default tracer

After the execution tracer overhaul described in #60773 is complete, we should make the v2 tracer the default version. This should involve: * Setting the v2 tracer as the default tracer. * Renaming all of the v2 files to be the default. * Removing the associated goexperiment flag. * Remove any lingering files that may no longer be in use.

@mknyszek

Comment From: gopherbot

Change https://go.dev/cl/576256 mentions this issue: runtime, cmd/trace: remove code paths that include v1 tracer

Comment From: gopherbot

Change https://go.dev/cl/576257 mentions this issue: runtime: rename v2 execution tracer files

Comment From: gopherbot

Change https://go.dev/cl/576258 mentions this issue: internal/goexperiment: remove the ExecTracer2 experiment

Comment From: cagedmantis

This work has been completed.